1. Field of the Invention
The present invention relates to a flexible display device, and more particularly, to a flexible display device which can achieve reliability against repeated bending and minimize damage to a display panel by reducing whitening, and a method of fabricating the same.
2. Description of the Conventional Art
Flat panel display devices have reduced weight and volume compared to cathode ray tube display devices. Typical flat panel display devices include liquid crystal displays, field emission displays, plasma display panels, organic light-emitting diode displays (OLED displays), and the like.
Among them, the OLED display is a self-emissive display in which an organic light-emitting diode provided on a display panel has high luminance and low operating voltage characteristics and emits light by itself. Hence, the OLED display has a high contrast ratio and can be made super-thin. Also, the OLED display can easily implement moving images due to its short response time of several microseconds (μs), has an unlimited viewing angle, and is stable at a low temperature.
Numerous efforts for implementing a flexible display device have been made in recent years to fulfill a variety of purposes such as the ease of carrying it around, versatility in configuration, damage prevention, etc. For instance, a screen-bendable flexible display device can be implemented by making a liquid crystal display or an organic light-emitting diode display of a flexible substrate.
FIG. 1A is a view schematically showing a structure of a related art flexible display device, and FIG. 1B is a pattern diagram of the force applied to the display device when the flexible display device of FIG. 1A is bent. Referring to FIGS. 1A and 1B, the related art flexible display device includes a plastic substrate 2, a driving element layer 3 formed on the substrate 2, a protective film layer 7 including a protective film for protection of the underlying layer, and a polarizing film layer 8.
The plastic substrate 2 is a base substrate where a variety of display elements and electrode patterns for implementing a display device are formed. The driving element layer 3 includes signal lines, thin film transistors, etc., and a display element layer made up of organic light-emitting diodes formed over or under the driving element layer 3.
Further, the protective film layer 7 serves to prevent damage to the driving element layer 3 caused by moisture penetration from the outside or impact, and the polarizing film layer 8 serves to compensate optical characteristics of the display device. The flexible display device of this structure bends to some degree when bent in the Y-axis direction. As it bends, a tensile force is applied outward and a compressive force is applied inward. Accordingly, the protective film layer 7 and the polarizing film layer 8 undergo changes in physical properties. Thus, whitening occurs in which white spots are seen on the surfaces, and the driving element layer 3 will suffer from such problems as damage to the thin film transistors, disconnection of the signal lines, and so on.